Questions tagged [computational-mathematics]
This tag concerns computational problems central to mathematical and scientific computing. The scope includes algorithms, numerical analysis, optimization, and linear algebra, computational topology, computational geometry, symbolic methods, and inverse problems.
2,003 questions
4 votes
1 answer
157 views
Converting an elliptic curve to Edwards form
Suppose $C$ is the plane curve cut out by the equation $$ u^2 + \frac{8}{3} uv + v^2 = \frac{5}{3} - u^2 v^2 . $$ Can you provide an explicit change of coordinates that puts this curve in Edwards form,...
0 votes
0 answers
117 views
How to solve the following system of equations without using inverse matrices?
I've got the following system to solve \begin{align} \begin{bmatrix} A & B \\ B^* & C \end{bmatrix} \begin{bmatrix} u \\ p \end{bmatrix} = \begin{bmatrix} 0 \\ g \end{bmatrix}, \end{align} ...
0 votes
1 answer
50 views
Computing large division fields of elliptic curves with CM
Let $E/\mathbb{Q}$ be an elliptic curve with complex multiplication by $\mathbb{Q}(i)$, e.g. any curve of the form $E:y^2 = x^3 + Ax$ with $A \in \mathbb{Q}^\times$. I would like to compute generators ...
2 votes
1 answer
76 views
Are there any other square-free Carmichael numbers $\leq10^8$ with two distinct positive two-cube representations besides $1729$?
I am checking an intersection of two properties: is a square-free Carmichael number, i.e. composite, square-free, and for every prime we have (Korselt). has two distinct representations as a sum of ...
0 votes
0 answers
52 views
Diffusion equation after one time-step
Consider the equation: $$ \partial_tu=D\partial_{xx}^2u $$ with reflecting boundary condition at $x=0$ and with $u(x,0)=\delta(x)$ as an initial distribution. First question: How should I understand a ...
2 votes
0 answers
47 views
How to overcome Cartesian/Polar round trip anomalies in 64-bit IEEE floating-point numbers
I'm working with a scriptable 3-D rendering tool that, due to various rounding and binary representation errors in point arithmetic will throw errors at extremely rare but always inopportune times. ...
2 votes
2 answers
94 views
Linear Program Duality Confusion
Consider the following Linear Program...$$\text{minimize}_{\vec x}\ \ \ \ x_1 - 2x_2 \\ \ \text{s.t.}\ \ \ \ \ \ 4x_1 + 6x_2 \leq 1 \\ x_2 \leq 7 \\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 3x_1 - x_2 = -2$$A ...
2 votes
1 answer
66 views
How to compute the derivative of transpose of inverse matrix of non symmetric matrix to matrix
I would like to calculate $$\frac{\partial (\mathbf F^{-1})^T}{\partial \mathbf F}$$ I know that $$\frac{\partial (F^{-1})_{ab}}{\partial F{ij}} = - (F^{-1})_{ai} \,(F^{-1})_{jb}$$ Also, if $[\mathbf ...
1 vote
0 answers
59 views
A scalable sieve generating long prime streaks
I have been experimenting with a family of Eratosthenes-like sieves that seem to generate long streaks of primes before producing the first composite. I would like to ask if something like this is ...
1 vote
0 answers
49 views
Algorithm for ideal sum/relative norm in multiquadratic field
I strongly suspect this question has a very straightforward answer. Let $M = \mathbb{Q}(\sqrt{a_1},\dots,\sqrt{a_k})$ be a large multiquadratic field. In this setup we assume it is infeasible to ...
0 votes
0 answers
55 views
How to calculate frame error rate of BCH Code in very high precision?
I want to calculate frame error rate(FER for short) of BCH Code in high precision, the formula is: $$FER = 1 - \sum_{i=0}^t {n \choose i} p^i(1-p)^{n-i}$$ where $n = 2560, t = 41$, $p = 10^{-4}$ to $...
-3 votes
1 answer
120 views
Why can't MS excel calculate -2^0.333, but it can calculate -2^(1/3)? [closed]
=(-2)^0.333 = #NUM! =(-2)^(1/3) = -1.25992 Is this a math thing or a coding thing? Why does expressing the power as a decimal produce an error, whereas as a fraction it finds the value?
3 votes
1 answer
101 views
Toric arrangements and system of polynomial equations
I am working on some problem on toric arrangements at the crossroad between topology, combinatorics and algebraic geometry. $\textbf{Setting}$ Let $m,n\geq1$ and let \begin{equation*}\mathcal{S}=\left\...
0 votes
0 answers
60 views
Volume/centroid of unit cube cut by plane
I need to calculate the volume (and centroid, but techniques for both seem to be fairly similar) of the intersection between the unit cube defined by $0 \leq x,y,z \leq 1$ and the halfspace defined by ...
1 vote
1 answer
275 views
Quickly determine (or approximate) surface area of intersection between an infinite plane and a trapezoidal prism
Problem A trapezoidal prism is "cut" by an infinite plane. The plane passes through the center of the trapezoidal prism, and the normal vector to the plane is known. The prism is isosceles (...